We are analyzing gene expression patterns in leukemia cells from patients with chronic lymphocytic leukemia (CLL) that we obtain from peripheral blood, bone marrow and lymph nodes. Our hypothesis is that the leukemic cells receive essential proliferation and survival signals in the bone marrow and/or lymph node. During the past year we have been able to isolate cells from more than 10 patients and have analyzed 8 matched pairs of bone marrow and blood derived CLL cells. Consistent with our hypothesis we found that CLL cells from the bone marrow showed a higher expression of genes associated with proliferation as well as a couple hundred genes that may relate to the specific signals induced in the leukemic cells by specific signals provided by the bone marrow microenvironment. Our current efforts aim at identifying the nature of these signals. From this we hope to identify which signaling pathways are essential for leukemic cell survival and which therefore could be good targets of new therapies. In a second part of the project we obtain CLL cells from patients who undergo therapy with two of the most active drugs in CLL therapy; rituximab and fludarabine. This therapy is given over a 6 day period and repeated every 4 weeks for 6 cycles. Patients donate blood every day during the first 6 treatment days and we analyze the changes in gene expression in these cells due to the therapy. We have collected and purified cells from 6 patients who have successfully been treated at NIH and we are about to initiate the gene expression analysis. These results will improve our understanding on how these drugs kill the cancer cells and may help to further improve therapeutic drug combinations.